1. Field of the Invention
Embodiments of the present invention generally relate to downhole tools and methods for operating downhole tools. More particularly, embodiments of the present invention relate to apparatus and methods for actuating downhole tools in response to perforating a downhole tubular. More particularly still, embodiments of the present invention relate to apparatus and methods for actuating a downhole valve using a chemically energetic charge.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit disposed at a lower end of a drill string that is urged downwardly into the earth. After drilling a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thereby formed between the string of casing and the formation. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas or zones behind the casing including those containing hydrocarbons. The drilling operation is typically performed in stages and a number of casing strings may be run into the wellbore until the wellbore is at the desired depth and location.
During the life of the well a number of downhole tools are used in order to maximize the production of different producing zones in the well. The casing is typically perforated adjacent a hydrocarbon bearing formation using a series of explosive or “perforating” charges. Such a series of charges are typically run into the well bore inside of an evacuated tube and that charge containing tube is known as a “perforating gun.” When detonated, the charges pierce or perforate the walls of the casing and penetrate the formation thereby allowing fluid communication between the interior of the casing and the formation. Production fluids may flow into the casing from the formation and treatment fluids may be pumped from the casing interior into the formation through the perforations made by the charges.
In many instances a single wellbore may traverse multiple hydrocarbon bearing formations that are otherwise isolated from one another within the Earth. It is also frequently desirable to treat such hydrocarbon bearing formations with pressurized treatment fluids prior to producing those formations. In order to ensure that a proper treatment is performed on a desired formation, that formation is typically isolated during treatment from other formations traversed by the wellbore. To achieve sequential treatment of multiple formations, the casing adjacent a lowermost formation is perforated while the casing portions adjacent other formations common to the wellbore are left un-perforated. The perforated zone is then treated by pumping treatment fluid under pressure into that zone through the perforations. Following treatment, a downhole plug is set above the perforated zone and the next sequential zone up hole is perforated, treated and isolated with an above positioned plug. That process is repeated until all of the zones of interest have been treated. Subsequently, production of hydrocarbons from these zones requires that the sequentially set plugs be removed from the well. Such removal requires that removal equipment be run into the well on a conveyance string which may typically be wire line coiled tubing or jointed pipe.
In the above described treatment process the perforation and plug setting steps each represent a separate excursion or “trip” into and out of the wellbore with the required equipment. Each trip takes additional time and effort and adds complexity to the overall effort. Such factors can be exacerbated when operating in wellbores that are not vertical and specialized conveyance equipment is often required in “horizontal” wellbores.
Therefore, there is a need for a capability of performing multiple downhole process steps in a single trip. Further, there is a need for a system that can perforate one zone and isolate another zone in the same trip. There is a need for a device that closes the bore of a casing upon receipt of an impulse from a downhole source. There is a further need for actuating downhole tools during a perforating operation. There is a need for a downhole isolation valve that can be actuated by an explosive charge.